Process and apparatus for rectifying alternating currents of electricity.



W. H. CHAPMAN.

PROCESS AND APPARATUS FOR RECTIFYING ALTERNATIN G CURRENTS 0FELECTRICITY.

APPLICATION FILED SEPT. 29' I915.

1,228,405. Patented June 5,1917.

w five nt MAM 5, 4 Wm UNITED STATES PATENT OFFICE.

WILLIAM H. CHAPMAN, OF PORTLAND, MAINE.

:enocnss AND APPARATUS FOR nnc'rxryme ALTERNATING CURRENTS orELECTRICITY.

Application filed September 29, 1915. Serial No. 53,198.

To all whom it may concern.

Be it known that I, WILLIAM H. CHAP- MAN, of Portland, in the county ofCumberland and State of Maine, have invented certain new and usefulImprovements in Processes and Apparatus for Rectifying AlternatingCurrents of Electricity, of which the following is a specification.

My invention relates to the production of constant polarity, hightension charges such as are required for X-ray work and for thecommercial deposition of solids from smoke.

Hitherto the production of such charges has been attended with greatdifficulty. The well known influence machines of Holtz, Toepler andWimshurst give excellent results for these uses if constructed on alarge scale with a multiplicity of glass plates to gain the quantity andvoltage required. But all of these machines'are too fragile and tooeasily put out of commission by damp Weather to be of extensivepractical use for these purposes.

Transformers on the other hand produce charges that are very stable inall weather conditions and the transformers themselves are naturallyrugged machines.

Many devices have therefore come into use to rectify the charges to beobtained from the transformers. All such devices hitherto constructedmake use of a suitably timed carrier to pick off the positive side ofthe alternating wave from a conductor having alternating charges in it.The direct charge so obtained is always of lower voltage than thealternating charge from which it originated and the charges are of apulsating character.

My invention is designed to provide means for multiplying up the voltageand of maintainin a uniform supply not subject to the pulsations offormer rectifiers, thus making the current equivalent in its steadinessto that of a Wimshurst or a Toepler machine while havin the quantity andstability characteristic of a transformer.

My invention consists essentially of delivering the negative ionsof thealternating charge through an intervening air space onto the surface ofthin insulating material which forms the dielectric element of acondenser.

The invention is based on the fact which I have discovered that if asheet of paper is laid down onto the surface of a grounded body ofconducting material like metal and a pointed conductor having analternating Specification of Letters Patent.

Patented June charge of several thousand Volts be brought near the paperbut separated therefrom 'b'y an interve'mng air space for an instant asit is in contact with the the paper when moved from the surface of theconductor will show a very high negative charge of many times thevoltage of the alternating charge. In fact a voltage of 100,000 voltsmay readily be produced in this manner by the use of an alternatingcharge of only 10,000 volts in the pointed conductor and the charge onthe paper is invariably negative.

The explanation of this fact may be involved in the known fact thatnegative ions have a higher velocity than positive ions and more of themwill therefore reach a given distant surface than of the positive ionsduring a single cycle of the alternating exciting charge.

Whatever the explanation may be, this principle has enabled me toconstruct an eflicient producer of constant polarity high potentialcharges operative under all weather conditions.

My invention may best be understood by reference to the accompanyingdrawing in which I have illustrated diagrammatically several differentmechanisms by which my invention may be carried out.

Referring to the drawing:

Figure l is a diagram showing the elements of my apparatus in simpleform,

Fig. 2 shows an arrangement for collecting the positive electricity,

Fig. 3 shows an arrangement of conductors for efi ecting a uniformdistribution of the charge over the surface of the paper,

Fig. 4 is an elevation of a machine using a disk in place of the bandused in the other forms shown and Fig. 5 is a section taken on the lineas w of Fig. 6%.

In carrying out my invention I make use of a thin sheet of insulatingmaterial which is arranged to be brought repeatedly into contact or intoclose proximity to a conducting body discharging the alternating chargewhich is to be rectified onto the sheet through a comb pointed conductorwhereby the air becomes ionized, the discharge taking place through agaseous medium while the sheet is in contact with the conducting body. Anegative charge of high potential will be generated on the surface ofthe sheet and is grounded conductor,

collected in the usual manner after the sheet separates from theconducting body.

In the preferable form of my apparatus I make use of a-pair of rolls ofconducting material over which runs an endless band of paper or otherinsulating material.

' Referring to the form shown in Fig. 1, 6 represents a continuous webof thin paper which may be .005 inch in thickness arranged to run overtwo metal rollers a and I) like a belt over two pulleys.

Comb points or conductors c and d are loon the combs 0 and d.

The rolls which are preferably grounded may be driven by any desiredmotive power and as the paper travels around it carries negative chargesfrom 0 and d to f and g and the direction of movement is immaterial.

An exciting alternating voltage at c and d of 10,000 will easilymaintain a constant direct voltage of 100,000 volts at f and g and thequantity of negative electricity thus supplied is proportional to thesurface of the paper presented to the rolls per minute.

If it is desired to produce positive electricity this is easilyaccomplished by means of the apparatus shown in Fig. 2. a

In this case the comb points f and 9 have extended surfaces or plates fand g located adjacent to the paper; The comb points j and k are locatedon the opposite-side of the paper from the plates f and g and areconnected with each other. The comb points j and k are grou ded and thesurfaces f" and g which are c arged with negative electricity inducepositive charges in j and is. These positive charges in j and k aredeliveredto the paper and are collected by comb points It and i. In thiscase where positive electricity is to be collected it is necessaryto'have the rolls run in a pre-determined direction. When a single combis used to deliver the negative charge to the paper as it runs over theroll, the charge is greater on some sections than on others, due to thefact that the section of paper that happens to be passing under thepoints during the positive alternation is receiving little if anycharge. A greater uniformity of charge is secured when two or more combsare used and placed some fraction of a cycle apart.

For example, suppose we are using a 60 cycle alternating current tosupply the exciting charge to the combs and suppose the paper isarranged to at a speed of 360 inches per second.

Then the paper moves six inches during the time of one cycle of the A.C. charge and if a single comb is used every alternate space. of threeinches will receive a maximum negative charge and the intervening spacesa minimum charge. If now we place two combs three inches apart or nineinches apart measured along the eripheral surface of the roll, a greateruni ormity of charge will be secured because every inch of the paperwill, during the passage over the roll come under one or the other ofthe combs during negative alternation of the exciting charge. I I

.In Fig. 3 I show the arrangement of two combs d and d for deliveringthe charge to the paper.

While the contact of the paper with the conductive surface is mostdesirable, my

process may becarried out without this contact. 7

Instead of abelt I may use a paper disk and have it run in very closeproximity to a solid grounded surface instead of being in actual contactwith it as in the forms already shown.

In Figs. 4 and 5 I show an arrangement where a paper disk is made torotate closely adjacent to a grounded-m etal plate.

Referring to Figs. 4 and 5, Z represents a disk of paper or otherinsulating material mounted on a shaft a supported on suitable bearingsand driven by a belt or other power. A grounded metal plate m ofrelatively large bulk as compared with the paper disk is set parallel tothe disk and as close as possible to it without touching. A conductor 19having comb points is located on the opposite side of the disk from thegrounded metal plate and connected with a source of alternating currentpreferably of 4,000 volts or more. A conductor 1' having comb points ispresented to the disk at a point where it is not backed by any solidmaterial. The conductors r and p are supported by a standard t ofinsulated material.

The arrangement may be varied if desired by connecting the rolls to thealternating exciting charge while the combs 0 and d are connected withthe ground. In this latter case the alternating charge on the rolls actsby induction on the grounded combs and causes them to deliver positiveand negative ions to the intervening air.

The negative ions will arrive in greater abundance on the surface of thepaper as is the case in the form shown in Fig. 1 and a negative chargewill be collected on the collecting conductors as shown in dotted linein Fig. 1.

It is to be understood that while I have described specifically certainforms which my invention may take them are many other forms which may bedeveloped as the principle of the invention comes to be understood anddeveloped for various purposes.

It is understood that in the drawings an alternating source ofelectricity which consists of discharging said charges in the form of aglow discharge to a body of relatively thin non-conducting materialbacked by a body of conducting material whereby ions of one sign aredelivered upon said thin material, se arating the materials fromeach-other and finally collecting the resulting charge.

2. The process of rectifying charges from an alternating source ofelectricity which consists of discharging said char es in the form of aglow discharge to a bo y of relatively thin non-conducting materialbacked by a body of conducting'material whereby.

ions of one sign are delivered upon said thin material separating thematerials from each other and finally collecting the resulting chargefrom the thin material.

3. The process of rectifying charges from an alternating source ofelectricity which consists of discharging said charges in the form of aglow discharge to a body of paper, backed by a body of metal, thenseparating the paper and metal and finally collecting the rectifiedcharge from the paper.

4. In an apparatus for rectifying alternating chargesof electricity thecombination of a thin sheet of insulating material and a conducting bodyso movable with relation to each other that portions of the sheet'willrepeatedly approach to a point adjacent to the conducting body andrecede therefrom, a conductor having small discharging points orsurfaces for delivering the alternating charge to the sheet while thesame is adjacent to the conducting body and means for collecting therectified charge from the sheet after it has receded from the conductingbody.

5. In an apparatus for rectifying alternating charges of electricity thecombination of a thin sheet of insulating material and a conducting bodyso movable with relation to each other that portions of the sheet willrepeatedly contact with the conducting body and recede therefrom, aconductor having small discharging points or surfaces for delivering thealternate charge to the sheet while the same is in contact with theconducting body and means for collecting the rectified charge from thesheet after it has receded from the conducting body.

(3. In an apparatus for rectifying alternating charges of electricitythe combination of a stationary conducting body, a movable sheet ofinsulatin material rotatin in such a position as to ring portionso itssurface repeatedly adjacent to said conducting body, a conductor havingsmall discharge points or surfaces for delivering the alternating chargeto the sheet while ad'acent to the conducting body and means orcollecting the rectified charge from the sheet when it is separated fromthe, conducting body.

7. In an apparatus for rectifying alternating charges of electricity thecombination of a pair of rolls of conducting material, a thin band ofinsulating material running over said rolls, a conductor having finepoints or surfaces for discharging the alternating charge onto said bandwhile in contact with one of said rolls and means for collecting therectified charge from said band while out of contact with said rolls.

8. In an apparatus for rectifying alternating charges of electricity thecombination of a pair of metal rolls, a paper band running over saidrolls, a conductor having fine points or surfaces for discharging thealternating charge onto said band whlle in contact with one of saidrolls and means for collectin the rectified charge from said band whileout of contact with said rolls.

' 9. In an apparatus for rectifying alternating charges of electricitythe combination of a pair of rolls of conducting material, a band ofinsulating material running over said rolls, a conductor having finepoints or surfaces for discharging the alternating charge onto said bandwhile in con tact with one of said rolls, a collecting conductor forcollecting the rectified charge from said band, a plate of conductingmaterial connected with said collecting conductor and positioned nearsaid band and a WILLIAM H. CHAPMAN.

